Cloudflare’s EmDash CMS (https://emdashcms.com/) is an interesting alternative to Wordpress. It’s been built from the ground up using modern technology, and fixes all of Wordpress’ pitfalls - secure plugins, deep AI integration, easy to install, and sensible built-in functionality (like forms). From my initial trials, it looks like it will eat Wordpress’ lunch soon enough.
People can be very religious about their WordPress dedication though, quality alone won’t do it. 
But yes since they promote EmDash for ‘blogs or microsites’ I think WordPress needs to be more worried than ConcreteCMS about it. Because WP is what people use when they don’t want to have to think about anything and just get it running quickly. ConcreteCMS’s ‘selling point’ is more the combination of a user-friendly CMS with a serious development framework that can be used for building specific functionality or even complex web applications.